This invention relates to tracheostomy tubes and assemblies.
Tracheostomy tubes are used to provide an airway directly to the patient's trachea via a surgically made opening in the neck. The patient end of the tube extends a short distance down the trachea and the machine end projects through the opening so that the patient can breathe freely via the tube. In some cases, the machine end of the tube has a coupling by which the tube can be connected to ventilating equipment. The tracheostomy tube should provide an efficient airway, it should be easy to insert and it should provide a minimum trauma to the patient. Tracheostomy tubes are generally of two different kinds. One kind of tube has a constant curvature along its entire length; the other has a straight section at its patient and machine ends and a curved section of constant radius between the two straight sections.
It is desirable for tracheostomy tubes to have a removable inner cannula or liner extending along the tube, the combination of the tube and inner cannula forming an assembly. The inner cannula is removed and replaced with a new cannula periodically, so as to dispose of any secretions that might have collected on the inside of the cannula. This reduces the risk of the accumulation of bacteria within the assembly and keeps the air passage clear without the need to remove the tube. The wall of inner cannula must be as thin as possible in order to minimize the obstruction to air flow along the assembly but the cannula must be sufficiently stiff to enable it to be inserted in the outer tube. Where the outer tube is curved along its length, the inner cannula can be made with the same curvature and can be inserted freely within the outer tube without deformation. Where the outer tube has straight sections at its ends, the inner cannula must be capable of flexing as it is inserted, so as to follow the shape of the outer tube. In order to ensure that the inner cannula does not buckle as it is inserted, the cannula may be corrugated, although this does reduce the air flow along the assembly. Examples of tracheostomy tubes are described in, for example, GB2251386, U.S. Pat. No. 5,222,487, EP474802, EP507886, GB2224213, GB2213384, GB2205504, GB2084023 and GB2056285.